CSI: Crime Scene Investigation is gearing up for their 14th season and the special 300th episode that comes with it.

The CBS procedural made its debut in October of 2000 and has been running strong ever since, despite some major casting changes in recent years. The milestone episode will see the return of an old character as a cold case makes the Las Vegas team think back to where they were 14 years ago.

"[The case] takes our characters back to the beginning," said executive producer Don McGill, according to TV Line. "They have to investigate a murder with the same M.O. and the same suspect from 14 years ago."

Making her first CSI appearance since season 12, Marg Helgenberger will reprise her role as Catherine Willows. However, it doesn't look like fans will get to see too much of Willows in real time. Instead Helgenberger's character will appear mostly in flashbacks, according to TV Line.

"We will flash back 14 years to seminal moments that show Catherine, Nick (George Eads), Sara (Jorja Fox), Greg (Eric Szmanda) and Ecklie (Marc Vann) as they were, [and how that] informed the evolution of the characters now," McGill told TV Line. "It's going to be a really fun episode, very emotional, that honors 14 years of CSI."